Italy
In Italy hitchhiking is a bit less common than in France or Germany, but it's very well possible.
Hitchhiking on the autostrada is not legal (there are big signs saying "NO autostop" at all highway entries), but it is unclear whether this extends to gas stations on the autostrada.
It is good to ask people in parking areas or at gas stations.
You can get a free map of whole Italy at almost every gas station (autogrill) with all gas stations listed in the map.
Communication
Even though most Italians say not to speak English they seem to understand a lot of English (and also Spanish).
Hitchhiking is autostop in Italian.
Just say autostop and your destination or show your thumb, otherwise they often think you are asking how to get somewhere, as Italy has a lot of tourists.
Safety
The northern part of Italy is safer than the southern part (south from Rome).
Border crossing
Italy is in the Schengen treaty.
Heading North
Take the Highway A23 (in the eastern part of Italy) to Austria (don't try to hitchhike through Switzerland, it's very difficult). Follow the A23 to Villach and Salzburg to get through the Alps very easy. On that way, you will also find a lot of people heading to Hungary, Slovakia and Slovenia.
Especially in summertime there are a lot of tourists from Austria and Germany. The new European plates start with a letter on the left side of the plate, representing the Country. Most Austrian (A on plate) and German (D on plate) are on the way to the sea or on their way back from holidays. So if you want to go North or South, try to find Germans or Austrians (they also speak better English than the Italians).
